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Saturday, August 18, 2012

A quick tour on Bluetooth

What is Bluetooth ?

­Bluetooth
takes small-area networking to the next level by removing the need for user
intervention and keeping transmission power extremely low to save battery power.

How its creates connection?

To Describe,let us consider the following :

You're on your Bluetooth-enabled cell-phoned, standing outside the door to your
house. You tell the person on the other end of the line to call you back in
five minutes so you can get in the house and put your stuff away. As soon as
you walk in the house, the map you received on your cell phone from your car's
Bluetooth-enabled GPS system is automatically sent to your
Bluetooth-enabled computer, because your cell phone picked up a Bluetooth
signal from your PC and automatically sent the data you
designated for transfer. Five minutes later, when your friend calls you back,
your Bluetooth-enabled home phone rings instead of your cell phone. The person
called the same number, but your home phone picked up the Bluetooth signal from
your cell phone and automatically re-routed the call because it realized you
were home. And each transmission signal to and from your cell phone consumes
just 1 milliwatt of power, so your cell phone charge is virtually unaffected by
all of this activity.

Bluetooth wireless PC card:

Bluetooth is essentially a
networking standard that works at two levels:

It provides agreement at the physical level --
Bluetooth is a radio-frequency standard.

It provides agreement at the protocol level,
where products have to agree on when bits are sent, how many will be sent
at a time, and how the parties in a conversation can be sure that the
message received is the same as the message sent.

The
big draws of Bluetooth are that it is wireless, inexpensive and automatic.The other way to get around wire is Infrared communication.Still it has two problem.1.Line of sight2.One to One technology.

Bluetooth is intended to get around the problems that
come with infrared systems. The older Bluetooth 1.0 standard has a maximum
transfer speed of 1 megabit per second (Mbps), while Bluetooth 2.0 can manage
up to 3 Mbps. Bluetooth 2.0 is backward-compatible with 1.0 devices.

How Bluetooth Operates?

Bluetooth networking transmits data via low-power radio
waves. It communicates on a frequency of 2.45 gigahertz (actually
between 2.402 GHz and 2.480 GHz, to be exact). This frequency band has been set
aside by international agreement for the use of industrial, scientific and medical
devices (ISM).

One of the ways Bluetooth devices
avoid interfering with other systems is by sending out very weak signals
of about 1 milliwatt. By comparison, the most powerful cell phones can transmit
a signal of 3 watts. The low power limits the range of a Bluetooth device to
about 10 meters (32 feet), cutting the chances of interference between
your computer system and your portable telephone or television. Even with the
low power, Bluetooth doesn't require line of sight between communicating
devices. The walls in your house won't stop a Bluetooth signal, making the
standard useful for controlling several devices in different rooms.

Bluetooth can connect up to eight
devices simultaneously. With all of those devices in the same 10-meter
(32-foot) radius, you might think they'd interfere with one another, but it's
unlikely. Bluetooth uses a technique called spread-spectrum frequency
hopping that makes it rare for more than one device to be transmitting on
the same frequency at the same time. In this technique, a device will use 79
individual, randomly chosen frequencies within a designated range, changing
from one to another on a regular basis. In the case of Bluetooth, the
transmitters change frequencies 1,600 times every second, meaning that more
devices can make full use of a limited slice of the radio spectrum. Since every Bluetooth
transmitter uses spread-spectrum transmitting automatically, it’s unlikely that
two transmitters will be on the same frequency at the same time. This same
technique minimizes the risk that portable phones or baby monitors will disrupt
Bluetooth devices, since any interference on a particular frequency will last
only a tiny fraction of a second.

When Bluetooth-capable devices come within range of one
another, an electronic conversation takes place to determine whether they have
data to share or whether one needs to control the other. The user doesn't have
to press a button or give a command -- the electronic conversation happens
automatically. Once the conversation has occurred, the devices -- whether they're
part of a computer system or a stereo -- form a network. Bluetooth systems
create a personal-area network (PAN), or piconet, that may fill a room
or may encompass no more distance than that between the cell phone on a
belt-clip and the headset on your head. Once a piconet is established, the
members randomly hop frequencies in unison so they stay in touch with one
another and avoid other piconets that may be operating in the same room. Let's
check out an example of a Bluetooth-connected system.

Why is it called
Bluetooth?

Harald Bluetooth was king
of Denmark in the late 900s. He managed to unite Denmark and part of Norway
into a single kingdom then introduced Christianity into Denmark. He left a
large monument, the Jelling rune stone, in memory of his parents. He was
killed in 986 during a battle with his son, Svend Forkbeard. Choosing this
name for the standard indicates how important companies from the Nordic
region (nations including Denmark, Sweden, Norway and Finland) are to the
communications industry, even if it says little about the way the technology
works.

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